Tuesday, 27 August 2013

Loop GDC Low-Float Shooting Head

 Please note:

I originally wrote this post in August 2013.  It was primarily a comparison between the GDC and the Rio AFS.  The AFS was an excellent line with very good presentation of smaller flies and lighter heads, but it was less happy with heavier tube flies and fast sinking polyleaders.  At that time the GDC offered a solution to the AFS' limited weight-shilfting capacity.  For the 2014 season Rio introduced the Scandi shooting head, which specifically addressed that deficiency with a minor compromise in presentation.

The GDC remains a very good head, but having used the AFS, GDC and Scandi for the whole of the 2014 season, the Rio Scandi is now my line of first choice.  The major points made in this post nevertheless remain broadly valid.

May 2016  

In my earlier post 'Half the System - Thinking About Lines' I stressed the critical role of the line in the overall performance and described some of the factors you should consider in making your choices.  If you're a novice and you haven't read it before, you might find it a useful introduction to this evaluation.

I purchased the GDC line from AM Angling for 2 reasons.  First, when testing the Loop Cross S1 it was fairest to include the line that Loop had most probably designed to complement the rod.  Second, I was looking for a successor heavy-fly and tip line to my old over-weight Windcutter that met a sad end on the Tweed in March, as recorded in the 6th Deadly Sin.

For the purposes of this assessment I used the Rio AFS as the comparator: it's very widely used and many anglers view it as a benchmark.  The GDC and the AFS have almost identical basic specifications (#9, 12m, 36/37 gm) yet on the river this evaluation showed that they are markedly different.

While it may be unconventional to put a recommendation first, but I wish to grab your attention: the evaluation shows that you should not buy a line solely on the basis of its specification of rating, length and weight, because your assumptions may be wildly incorrect.

Making a Line

Remarkably few companies actually manufacture salmon fly lines: in UK sales Airflo (Wales), Rio (USA) and 3M/Scientific Anglers (USA) occupy most of the market.  Brands like Loop, Guideline, Hardy and MacKenzie do not make the lines that carry their names, but use various specialist manufacturers as sub-contractors to make lines to their specification, developing products jointly.  To complicate matters the same manufacturers also sell products directly.  Consequently, 3 or 4 makers underpin most of the 12 or so brands that you see in the tackle shops.  It's quite a detective problem to identify who really makes what for whom, and I found no clues on the GDC's packaging.  The fact that Rio also uses the term 'density compensation' may just be coincidental.  

Although there are some very clever technologies used in fly lines, their range is narrow. For example, there are 2 primary coatings employed: PU, which only Airflo uses; and the various sub-types of PVC that the others favour.  So you will encounter many lines that share common foundations and therefore embody the same or very similar technology.  The big differentiation within classes of line arise not through technology, but from design - mainly taper and weight distribution - as this assessment confirmed, so I'm not unduly concerned by my failure to identify who actually makes the GDC (the running line is of US origin).  Frankly, it's not that important: by the time you've combined the effects of length, taper, weight distribution and the limitations of your casting on a line, who made it with what technology becomes a lesser issue.

This axiom does not restrain the sellers of salmon fly lines.  You have to feel a certain sympathy for them, because they've given us super products, which with due care and an annual wash will last at least 10 years.  This is an accelerated version of the flawed business model that put the makers of English shotguns out of business.  You don't get much repeat business if your product lasts a a hundred years, as Ford tried (unsuccessfully) to convince Volvo during their ownership. Overcoming this flaw and stimulating the market in order to survive is is the reason why the line makers change everything bi-annually.  Rio are the masters of the art: as soon as everyone agreed the Windcutter (and the AFS in its turn) was brilliant, it disappeared from the range.  Don't worry, the Windcutter is coming back next year under a new name - 'Short Spey' - but the AFS has vanished from their 2014 catalogue. Obviously there's not much to do in Idaho in winter.

GDC - Gradual Density Change and the 'V' Loop

The video on the Loop Blog explains that the GDC's key design driver is the performance of sinking heads with varying sink rates along their length.  Loop claim that by changing the density of the line coating progressively you can have both uniform sinking properties and preserve the effects of the taper on the line's flight.  As I don't need or use sinking heads I'll leave others to pronounce on their underwater performance.  My interest in this assessment focused on the GDC's casting and flight qualities, even though I remain incapable of equalling the extraordinary loops that Tomas Ögren generates in the film (helpfully someone has photo-enhanced the line in the otherwise rather grey images to highlight the 'V' shape).  Hr Ögren is a professional who no doubt has spent lots of time perfecting the trick: I doubt any normal angler will ever see it, nor should they expect this line to do it for them without the statutory 10,000 hours of practice.  You can't buy that level of performance for £60 (or even £600 for that matter).

On the other hand, as a Yorkshireman I really like Tomas' laconic style and the absence of hype.  It's the Volvo school of car sales: "you'll survive the crash".  Not even the 'V' loop cracks a smile.  He must have relatives in Barnsley: "eeh, it's not a bad line this".  Come to think of the history, he's probably got relatives all over this county, especially around the City of Jorvik, including my wife, as evidenced by her family's height and hair colour.

The taper design shown on the Loop website looks like this, with the reel end to the left. Actually it isn't like this, because the taper on most of the body is imperceptible.  Indeed it appears parallel to the naked eye (I didn't resort to a micrometer), with a fairly sharp taper towards the front, which I regard as traditionally Scandinavian.  This gradual taper is readily apparent in the sequence of photos in the next section.

GDC and AFS Compared

In all of the frames the AFS is at the top.

At 1m the pronounced diameter of the AFS is very clear.

And at 3m, where the GDC is unchanged..

The AFS transitioned into taper at 4.2m so here at 5m it is now slimmer than the GDC, which shows only limited reduction.

The 6m point roughly equates to the top half of the D loop in a Single Spey.

At 7m the AFS has slimmed further, whilst on the GDC the first visible indications of taper are becoming apparent......

...but not a lot.

However, at 11m (of 12) the GDC's taper comes in earnest.  At the tip there's not a big difference between them.

This adds up to a very big differentiation between the 2 lines in their distribution of mass. The AFS packs a lot of weight into the 6m that comprise the top half of the D loop, whereas the GDC spreads it across 80% (i.e. almost all the available length not in contact with the water in a full Single Spey).  In turn this creates significant differences in the ways in which the 2 lines load the rod, accelerate, take off, fly and turn over; and their capacity for shifting weight in the form of heavy tips and flies.  To understand the physics it helps to remember that in the initial stage of the forward cast the line at the top of the D loop is accelerating forwards, whereas the bottom half is trying (but failing) to go in the opposite direction.  Although the GDC is clearly optimised towards the Scandinavian underhand style, the prolonged loading that results from its weight distribution favours a through action rod rather than the faster tip-biased stereotype and a small injection of British style (observe Tomas' top arm extension in some of the casts).

Test Format

Using the 14' #9 Loop Cross S1 I ran through a succession of test serials with both the GDC and AFS.  These started with a small fly (#12) on a plain 10' fluorocarbon leader and progressed through increasingly heavy flies and sink tips.  The ultimate test involved a 12' very fast sink tip and weighted tube.  At intervals I also sampled the various configurations with the 14' #9 Loop Classic to establish whether there was backwards compatibility between the previous generation rod and the latest line.   The Classic handled the GDC well but I didn't do enough exploration to be able to declare it an ideal partnership.

The conditions were fair with a 10-12 mph/15-18 kph swirling wind, which was predominantly downstream for the longer range work.  The flow and eddy patterns in the upper half of the first pool (Frodle Dub) presented a  number of complex challenges for line extraction and pick-up, whereas the second pool (Flesh Dub) had uniform flow across the entire 40m width and opportunities for testing performance at different wading depths up to waist level.

On the Water - Impressions

In use these 2 lines are markedly different: I had to allow myself a period at the start of each serial to adjust and adapt.  This didn't make for perfect testing or the best use of time, so towards the end I had a prolonged session with the GDC alone to consolidate my thoughts. What follows are headline summaries of each point, from the perspective of an adequate caster:

  • You need to learn and apply some slightly different (Swedish) tricks to get the best out of the GDC.  If you have a traditional British casting style you may be disappointed at first, because you were not uppermost in the designer's mind.  Stick with it because the GDC's many virtues do not jump straight out of the box.
  • If you want nice presentation of smaller flies on plain leaders in shallow water, the AFS wins hands down. Indeed, I gained the impression that this criterion did not feature highly in the GDC's design brief.  
  • The GDC's turnover is good and gets better still as the fly weight increases.  At shorter ranges slowing the running line is essential to prevent the GDC's momentum creating a hard stop and consequent 'spring back' of the fly.
  • Up to and including the shorter (5') and lighter sink tips there was nothing to choose between the 2 lines in terms of distance capability.
  • Once I entered the heavier and longer (10') tip and fly range, the GDC came into its own.  Its shifting power from water-borne sustained anchor casts like the Snap T and Double Spey is remarkable and goes some way into Skagit country.  That also translates into excellent deep wading performance: covering the entire fishing width of Flesh Dub from top-thigh depth with a 14' rod is not something I've done before.  
  • As I noted in the S1 assessment, the more weight you stick on the front of the GDC, the further and faster it goes.  Like a Gotenburg barmaid, it's not sophisticated but has obvious attractions and serious muscle, although I didn't extend the simile by trying to cast a crate of Pripps (2 or 3 cans would have been welcome at lunchtime).
  • Those characteristics make the GDC steady as a rock across and powerful into the wind, scenarios in which the AFS' fine tip can often be a handicap for the less experienced caster, especially at longer range.
  • I found the AFS easier to use in airborne anchor casts, principally the Single Spey and Snake Roll, on account of its more helpful weight distribution.  That is more of a reflection on the ease of the AFS than any difficulty or deficiency in the GDC.  Given another 30 minutes of practice and tuning my use of the GDC with both casts would have improved substantially.  Unless you're highly experienced with a wide range of lines you need time to get it right with one that's unfamiliar.
  • Initially at least the GDC responded best to the Scandinavian style of Single Spey: although my Swedish doesn't get a lot of practice I did manage some very respectable loops.  More 'U' than 'V' perhaps, but they were certainly much better than 'L' or 'O'.
  • In a downstream wind with the GDC I found Double Spey consistently superior to the Snake Roll.  However, in a left bank, left shoulder situation you rapidly become aware of the amount of clearance you need behind you to employ the full power of the GDC in a 45 degree Double Spey cast.
  • The manufacturing quality and surface finish of the GDC was first class and entirely free of imperfections or anomalies.
  • Whilst not part of the test, the Loop Runner was entirely satisfactory: in a whole day's casting I didn't have a single tangle or stoppage.  Its shade of red showed up well on the water through both green and yellow Polaroids.  It has a nice big end loop that accommodates a coiled or spooled head. 
  • I never worked out how 'low floating' was different to 'floating'.

The Bottom Lines

The GDC is clearly designed for wide, strongly flowing, cool rivers and consequently larger flies and heavier tips.  I have no doubt that the #10 and the 15' Cross S1 would deliver them over a fearsome acreage of water.  This is a line for spring and autumn, when its formidable weight shifting ability brings welcome flexibility to your tip and fly choices.  For several years I used an over-weight Windcutter in this role until its sad demise on the Tweed in March, which left me bereft for want of an obvious replacement.  For me the GDC meets that requirement in full and I look forward to using it just as soon as we have some water.

I'm aware that the Guideline, Airflo and McKenzie heads might have been contenders for my requirement. Certainly they all have their enthusiastic users and proponents, but if you're looking for such heads you should now add the GDC to your options and testing list.  But they're not all the same.  To avoid disappointment you need to be clear what role you wish the line to perform in what fishing conditions, and test against those criteria.  Only then can you say objectively whether A or B is better.

If you have the GDC you may not need a Skagit head unless you fish with tightly constrained back-cast space and a fly like crate of Pripps on the end of a T14 tip.  This helps to relieve the impact of the GDC's £60 price tag, but many salmon fisherman, true to type, will buy a Skagit anyway.

I suggest that this is not the ideal line for beginners and early novices owing to the adaptations to technique it requires for optimum performance.  Line profiles like the AFS make for easier learning and a quicker development of confidence across a wider selection of casts.  

Even for more experienced casters, do not expect the GDC to give unbridled joy with the first cast. Take time with it, and if it's not working, it's you, not the line.  Once you've got yourself in union with the GDC it really starts to show its worth.

The very wide differences between the 2 lines in this evaluation with almost identical specifications of rating, length and weight reinforces the truism - TRY BEFORE YOU BUY, AND TAKE YOUR TIME OVER DOING SO.


  1. Having just come upon this article while I'm considering purchasing the GDC Float to go with the Goran Anderssen 12' 6/7 two-hander I was given for Christmas...I have to say that this is probably the best article I've ever read regarding any fly line. One of my favorite bits is "Take time with it, and if it's not working, it's you, not the line.". That's been my observation, personally, for 25 some odd years of fly fishing, it's me, not the equipment and I adjust accordingly. I am a beginner to a two-hander. So, I have nice things to look forward to with this rod and line. Thanks for the article.
    ghetto fly fishing

    1. Cliftz, many thanks for your kind words: such encouragement is always welcome. I wish you all good fortune with your journey into the realm of double handed casting, but do take professional lessons, which will make it all much easier and more enjoyable. If you're a novice in the 2 handed business then the Rio Scandi may be a better start point than the GDC as I noted in the article. You'll find a 12' double hander sheer delight.
      Happy New Year and tight lines.